A three-year-old US toddler has died after shooting herself with a loaded gun that she mistook for a Wii controller, media reports say.

Cheyenne Alexis McKeehan, her stepfather Douglas Cronberger and mother Tina Ann were in their mobile home in Tennessee in south-east USA on Saturday night when Mr Cronberger thought there was someone outside.

He took his unloaded gun out of a cabinet, loaded it and left the home to look for the suspected prowler, The Tennessean reported.

When he returned, he placed the loaded .380 calibre pistol on a living room table and forgot about it, a police statement said.

Mistaking the gun for a Nintendo game controller that she had been playing with for days, Cheyenne picked up the weapon and shot herself in her abdomen. Her mother was just a few metres away on the computer, police said.

She was brought to hospital but was pronounced dead soon after she arrived.

"The big message we're trying to tell parents is if you've got a gun, put it up, especially if you have children," Wilson County Sheriff Terry Ashe was reported as saying.